A lizard may seem at first like an unassuming monster, but in fact it is very helpful to any aspiring adventurer.

Killing a lizard always leaves a corpse. Eating lizard meat, whether from a corpse or a tin, will cure stoning from a cockatrice, and a live lizard is completely invulnerable to this method of attack. It is usually better to eat the corpse since opening a tin may take many turns, and lizard corpses do not rot and never become old to cause sickness. Because of this, it is wise to keep at least one lizard corpse in your inventory.

When playing during new moon, cockatrice hissing always begins the stoning process, unless a lizard corpse is carried in main inventory; with the corpse, the chance of stoning is restored to normal.[1]

A less useful effect of eating a lizard corpse is that it sets the remaining turns for confusion and stunning to two turns. As these effects are trivial, a far better use for the corpse is to stave off instadeath by stoning from a cockatrice.

Note that only actual lizard corpses will stop stoning; while other monsters represented by a colon [:], such as newts and geckos, are technically "lizards", their corpses do not share this property.

The monster ate a lizard corpse to cure stunning or confusion. (The "slowing down" message appears incorrectly in this case because the "eat a lizard corpse to unstone" function is called. This also means that a monster with intrinsic speed loses it if it eats a lizard corpse.[2][3])

Lizards first appear as live animals in NetHack 3.0.6, but the corpses occur as random objects in prior versions, all the way back to Hack 1.0. Stoning by hissing is an instadeath before Hack 1.0.3, and lizard corpses reduce confusion rather than affecting stoning. Hack 1.0.3 introduced gradual stoning and made it possible for lizard corpses to halt the stoning.

Lizards, snakes and the burrowing amphisbaenids make up the
order Squamata, meaning the scaly ones. The elongate, slim,
long-tailed bodies of lizards have become modified to enable
them to live in a wide range of habitats. Lizards can be
expert burrowers, runners, swimmers and climbers, and a few
can manage crude, short-distance gliding on rib-supported
"wings". Most are carnivores, feeding on invertebrate and
small vertebrate prey, but others feed on vegetation.